US20090295638A1 - Use of a measurement signal evaluation means of a position measuring device to determine the time difference between a first event and a second event - Google Patents

Use of a measurement signal evaluation means of a position measuring device to determine the time difference between a first event and a second event Download PDF

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Publication number
US20090295638A1
US20090295638A1 US12/471,858 US47185809A US2009295638A1 US 20090295638 A1 US20090295638 A1 US 20090295638A1 US 47185809 A US47185809 A US 47185809A US 2009295638 A1 US2009295638 A1 US 2009295638A1
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event
signal
time difference
periodic
values
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US12/471,858
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Roland Finkler
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Siemens AG
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Siemens AG
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Assigned to SIEMENS AKTIENGESELLSCHAFT reassignment SIEMENS AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FINKLER, ROLAND
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G—PHYSICS
    • G04—HOROLOGY
    • G04F—TIME-INTERVAL MEASURING
    • G04F10/00—Apparatus for measuring unknown time intervals by electric means
    • G04F10/06—Apparatus for measuring unknown time intervals by electric means by measuring phase

Definitions

  • the present invention relates to a measurement signal evaluation of a position measuring device.
  • a periodic square-wave pulse signal which is generated by a clock generator is usually used for this purpose.
  • the time difference between the two events is determined from the number of square-wave pulses between the two events.
  • the resolution of the time difference between two events is thus limited by the frequency at which the square-wave pulses are generated by the clock generator.
  • the higher the intended temporal resolution of the determined time difference the higher the selected frequency of the square-wave pulse signal must be. If a very high resolution is intended to be achieved, the frequency of the square-wave pulse signal must accordingly be selected to be high, that is to say the square-wave pulses follow one another at very short intervals of time.
  • square-wave pulse signals at a high frequency produce electromagnetic interference which may result in malfunctions, in particular in electrical components arranged in the vicinity.
  • time difference between two events can be measured by sampling a linearly rising voltage, for example by sampling the voltage across a capacitor which is charged using a current source.
  • a time measurement is relatively inaccurate.
  • two signal transmitters In commercially available position measuring devices for measuring a position, for example, of a movable machine element, for example a motor shaft, two signal transmitters generally scan a movable material measure and, in a manner corresponding to the graduation arranged on the material measure, generate periodic signals which are used to determine the current position of the machine element with the aid of a measurement signal evaluation means.
  • An example of such a position measuring device is described in German Pat. No. DE 10 2004 038 621 B3, whereby a position is determined from two sinusoidal signals, which have a phase offset with respect to one another, using a measurement signal evaluation means.
  • Two signal transmitters scan the material measure graduation and output the two sinusoidal measurement signals which have a phase offset with respect to one another.
  • the two measurement signals are then sampled in a fixed time frame using two analog/digital converters.
  • a downstream measurement signal evaluation means determines the position signal from the two measurement signals which have been digitized in this manner.
  • the measurement signal evaluation means subjects the measurement signals to analog/digital conversion on the input side and outputs the position signal determined by it on the output side.
  • a measurement signal evaluation means which determines a position signal, i.e. a position, from two or more measurement signals.
  • German patent document DE 27 29 697 A1 discloses a measurement signal evaluation means of a position measuring device to determine a position signal from two measurement signals.
  • such commercially available measuring devices often also include, for example, special methods for compensating for and/or correcting offset, amplitude, phase and harmonic errors in the measurement signals in order to increase the accuracy of the position determined.
  • a method for determining a time difference between a first event and a second event includes the steps of determining a first position value from a first periodic signal that is triggered when the first event occurs, determining a second position value from a second periodic signal that is triggered when the second event occurs, and determining the time difference from a difference between the first and second position values.
  • a position measuring system includes a measurement signal evaluation means for determining a time difference between a first event and a second event, the measurement signal evaluation means configured to determine a first position value from a first periodic signal that is triggered when the first event occurs, determine a second position value from a second periodic signal that is triggered when the second event occurs, and determine the time difference from a difference between the first and second position values.
  • q position measuring system includes a first signal generator signal producing a first periodic signal, a first A/D converter receiving the first periodic signal, a second signal generator signal producing a second periodic signal, a second A/D converter receiving the second periodic signal, an OR gate receiving a first trigger signal produced by an occurrence of a first event, and a second trigger signal and second event respectively, and transmitting the first and second trigger signals to corresponding trigger inputs of the first and second A/D converters and producing first and second triggered output signals that correspond to the periodic signals at a time of the first and second event, and an evaluation unit receiving at a first input the first triggered output signals corresponding to values of the first periodic signal for the first event and the second event, and receiving at a second input the second triggered output signals corresponding to values of the second periodic signal for the first event and the second event, the evaluation unit having an output that generates position values to be used for determining the time difference from a position difference between the first and second position values.
  • the present invention resolves prior art problems by determining the time difference through determination of the positional difference between the first position value and the second position value and weighting the positional difference with a proportionality factor. This ensures simple determination of the time difference. It also proves to be advantageous if the periodic signal is generated using a signal generator assigned to the periodic signal or the periodic signals are generated using signal generators assigned to the periodic signals. This makes it possible to generate the periodic signal or the periodic signals in a particularly simple manner.
  • the periodic signal or the periodic signals is/are sampled solely when the first and second events occur in order to generate input values for the measurement signal evaluation means. This makes it possible to use the measurement signal evaluation means in a simple manner.
  • time difference determined in this manner is used to determine the position of a movable magnet in a magnetostrictive position measuring device.
  • a high temporal resolution is required, in particular, in magnetostrictive position measuring devices.
  • FIG. 1 shows an exemplary embodiment of the invention
  • FIG. 2 shows two periodic signals
  • FIG. 3 shows a diagrammatic illustration of a commercially available magnetostrictive position measuring system
  • FIG. 4 shows the determination of a position from the time difference determined
  • FIG. 5 shows another exemplary embodiment of the invention.
  • FIG. 1 shows a diagrammatic illustration of an exemplary embodiment of the present invention.
  • a first signal generator 1 generates a first periodic signal x 1 (t) and a second signal generator 2 generates a second periodic signal x 2 (t).
  • the two signals x 1 (t) and x 2 (t) are sinusoidal and are temporally offset with respect to one another.
  • the two signals may also have other signal waveforms which are not sinusoidal.
  • the two signals need not necessarily have the same signal waveform. However, they should preferably not have a square-wave signal waveform.
  • the two signals x 1 (t) and x 2 (t) are supplied, as an input variable, to the respectively associated analog/digital converters 11 and 12 .
  • a gate pulse i is respectively generated at the output of a logic OR gate 13 , which pulse causes the two analog/digital converters 11 and 12 to respectively sample the analog signals x 1 (t) and x 2 (t) once.
  • the occurrence of the first event A and of the second event B is supplied in this case to the OR gate 13 in the form of a respective trigger pulse as an input variable.
  • the two analog/digital converters 11 and 12 thus generate the signal values x 1 (t a ) and x 2 (t a ) sampled at the time t a at which the first event A occurs and the signal values x 1 (t b ) and x 2 (t b ) sampled at the time t b at which the second event B occurs.
  • the signal values x 1 (t a ) and x 2 (t a ) and the signal values x 1 (t b ) and x 2 (t b ) are then supplied, as input values, to a measurement signal evaluation means 3 which is known from the prior art and carries out the measurement signal evaluation already described.
  • the measurement signal evaluation unit 3 determines a position value f A from the two signal values x 1 (t a ) and x 2 (t a ) and a position value f B from the two signal values x 1 (t b ) and x 2 (t b ).
  • the measurement signal evaluation which is carried out in the measurement signal evaluation unit 3 corresponds, for example, to the measurement signal evaluation disclosed in German patent document DE 10 2004 038 621 B3, with the difference that in accordance with the invention, the two signal transmitters, as described in German patent document DE 10 2004 038 621 B3 and the material measure are replaced with the two first and second signal generators 1 and 2 indicated in FIG.
  • the two analog/digital converters are driven in such a manner that they no longer sample the signals in a fixed time frame (for example every 0.125 ms) but rather only once when the first event A occurs and once when the second event B occurs.
  • the two signal generators generate periodic signals with a period duration which is always constant and consequently at a frequency which is always constant.
  • the position values f A and f B in FIG. 1 of the present application correspond to individual values of the position signal as referred to in German patent document DE 10 2004 038 621 B3.
  • the measurement signal evaluation means could also be in the form of the measurement signal evaluation means, as described for example in German patent document DE 27 29 697 A1.
  • any measurement signal evaluation means (which is known from the prior art) of position measuring devices to implement the invention, the signal generators having to generate signals which are adapted to the respectively used measurement signal evaluation means and can be processed by the respectively used measurement signal evaluation means.
  • the position values f A and f B determined in this manner are supplied, in a next step, to a positional difference determination unit 4 as an input variable.
  • the positional difference determination unit 4 calculates the positional difference ⁇ between the first and second position values by subtracting the first position value f A from the second position value f B according to the relationship
  • the positional difference determination unit 4 outputs the positional difference ⁇ determined in this manner to a multiplier 5 within the scope of the exemplary embodiment, said multiplier weighting the positional difference ⁇ by multiplying it by a proportionality factor C within the scope of the exemplary embodiment.
  • the proportionality factor C depends on the frequency f of the periodic signals x 1 (t) and x 2 (t) and, provided that the two signals x 1 (t) and x 2 (t) are at the same frequency f and are sinusoidal and are temporally offset with respect to one another, results, for example, as:
  • the positional difference ⁇ determined is converted into a corresponding time difference T and is output at the output of the multiplier 5 .
  • the time difference T determined in this manner can then be processed further in any desired manner according to the respective technical requirements.
  • FIG. 2 again illustrates, by way of example, a simple generally known implementation of the functionality of the measurement signal evaluation unit 3 , the two periodic signals x 1 (t) and x 2 (t) being plotted against the position, which is given by the angle
  • the number q of zero crossings of the signals x 1 (t) and x 2 (t) between the events A and B is also determined. q is then increased by 1 if the first zero crossing counted
  • q ⁇ 1 indicates the number of quadrants of the signals x 1 (t), x 2 (t) which have been completely passed through between the events A and B.
  • the possible corrections by +1 or ⁇ 1 according to the first and last zero crossings counted are necessary in this case because measurement inaccuracies may result in inconsistencies both between the first zero crossing counted and the quadrant determined for f A and between the last zero crossing counted and the quadrant determined for f′ B .
  • DE 27 29 697 A1 uses a direction discriminator and an electronic up/down counter since there the process does not start from a sin/cos transmitter which rotates at a constant angular velocity but rather must also take changes in the direction of rotation into account.
  • the invention can be used in a particularly advantageous manner in position measuring systems for measuring a position, for example in magnetostrictive position measuring systems in which it is necessary to accurately determine the time difference between two events, which occur after one another in a short period of time, in order to determine a position.
  • FIG. 3 illustrates the principle of commercially available magnetostrictive position measuring systems.
  • a magnet which is preferably in the form of an annular permanent magnet 7 is moved along a measuring rod 8 , which is guided through the permanent magnet 71 , along the direction of movement X.
  • sensor electronics 6 determine the position x(t), that is to say the position of the permanent magnet 7 .
  • the sensor electronics 6 generate, in a fixed timing pattern (for example one millisecond), starting pulses 9 which pass through the measuring rod 8 as current pulses.
  • the magnetic field carried along by the current pulse produces mechanical torsion in the measuring rod 8 at the position of the permanent magnet, which torsion produces a structure-borne sound wave, which runs back to the sensor electronics 6 , inside the measuring rod 8 .
  • the arrival of this structure-borne sound wave is recorded in the sensor electronics 6 and is converted into a stopping pulse 10 .
  • the time difference T between the starting pulse (corresponds to event A) and the associated stopping pulse (corresponds to event B) is proportional to the position x(t) of the permanent magnet 7 .
  • the time difference T is multiplied by a constant K using a multiplier 6 , the constant K resulting from the speed of the structure-borne sound wave in the measuring rod 8 whilst disregarding the propagation time of the electrical starting pulses 9 .
  • the time difference T to be determined between the starting pulse, which represents the first event A according to FIG. 1 and the associated description, and the associated stopping pulse, which represents the second event B according to FIG. 1 is very small in this case, in particular in the case of magnetostrictive position measuring systems. Therefore, the use of the invention is particularly suitable for magnetostrictive position measuring systems since, as already stated, the time difference T to be measured between the two events is very small and a high square-wave pulse signal frequency (100 MHz or higher) is consequently needed for the time measurement in order to measure the time difference in commercially available magnetostrictive position measuring systems if a high resolution of the time measurement is intended to be achieved.
  • this high-frequency clock signal which is required in commercially available magnetostrictive position measuring systems is a source of electromagnetic interference which, in particular, interferes, for example, with the sensitive sensor electronics 6 (according to FIG. 3 ) of the magnetostrictive position measuring system.
  • the relatively low-frequency (for example 0.5 MHz or lower) periodic signals x 1 (t) and x 2 (t) are needed with the aid of the invention, which signals produce considerably less electromagnetic interference on account of their considerably lower frequency and their sinusoidal shape instead of a square-wave shape.
  • the interference caused by the necessary time measurement can thus be reduced by the invention.
  • the invention can also be used in other types of position measuring systems which are based on the measurement of a propagation time, that is to say in other types of position measuring devices which are based on the measurement of a propagation time.
  • Magnetostrictive position measuring systems are disclosed, for example, in U.S. Pat. No. 5,334,933, U.S. Pat. No. 3,898,555 and European patent document EP 0 442 985 B1. Furthermore, magnetostrictive position measuring systems are disclosed in the book entitled “Lineare Weg-und Abstandssensoren” [ Linear Displacement and Distance Sensors], 2004, ISBN 3-937889-07-8, pages 53 to 66.
  • Magnetostrictive position measuring systems are also disclosed, for example, in a leaflet entitled “Magnetostritechnische, Physikalische Kunststoffn” [Magnetostriction, Physical Principles] from MTS Sensors which is disclosed on the web page www.mtssensor.de/fileadmin/medien/downloads/mts_mess flick.pdf.
  • FIG. 5 illustrates another exemplary embodiment of the present invention.
  • the basic structure and method of operation of the embodiment illustrated in FIG. 5 essentially correspond to those of the embodiment described above in FIG. 1 . Therefore, in FIG. 5 , the same elements have been provided with the same reference symbols as in FIG. 1 .
  • the fundamental difference is that, in the embodiment according to FIG. 5 , only a first periodic signal x 1 (t) and consequently also only a first signal generator 1 are needed to determine the time difference T.
  • the circuit illustrated in FIG. 5 is extended with a further logic OR gate 14 , which ORs its input signals, and a time delay element 15 , which delays its input signal by the period of time T V , and two switches 16 and 17 .
  • the signal x 1 (t) is supplied to the analog/digital converter 11 as an input variable.
  • a gate pulse i is respectively generated at the output of the logic OR gate 13 , which pulse is forwarded via the OR gate 14 and causes the analog/digital converter 11 to respectively sample the analog signal x 1 (t) once.
  • the occurrence of the first event A and of the second event B is supplied in this case to the OR gate 13 in the form of a respective trigger pulse as an input variable.
  • the analog/digital converter 11 thus generates the signal value x 1 (t a ) sampled at the time t a at which the first event A occurs and the signal value x 1 (t b ) sampled at the time t b at which the second event B occurs.
  • the time delay element 15 causes the analog/digital converter 11 to carry out a further sampling operation, which is temporally offset by the period of time T V , and thus to generate the signal values x 1 (t a +T V ) and x 1 (t b +T V ) on the output side.
  • the switches 16 and 17 are used to output the signal values x 1 (t a ), x 1 (t a +T V ), x 1 (t b ) and x 1 (t b +T V ) to the measurement signal evaluation means 3 as input values, the switches 16 and 17 switching their input signal through to their output when a logic “1” occurs at their control input S.
  • the signal value x 1 (t a +T V ) corresponds to the signal value x 2 (t a ) according to FIG. 1 and the signal value x 1 (t b +T V ) corresponds to the signal value x 2 (t b ) according to FIG. 1 .
  • the method of operation of the embodiment according to FIG. 5 corresponds to the method of operation of the embodiment according to FIG. 1 .

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)
  • Measurement Of Unknown Time Intervals (AREA)
US12/471,858 2008-05-27 2009-05-26 Use of a measurement signal evaluation means of a position measuring device to determine the time difference between a first event and a second event Abandoned US20090295638A1 (en)

Applications Claiming Priority (2)

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EP08009649A EP2128570A1 (de) 2008-05-27 2008-05-27 Verwendung einer Messsignalauswertung einer Lagemesseinrichtung zur Ermittlung der zeitlichen Differenz zwischen einem ersten Ereignis und einem zweiten Ereignis
EPEP08009649 2008-05-27

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US20100250184A1 (en) * 2008-03-18 2010-09-30 Satoshi Kawamura Rotation angle detection apparatus
CN103092061A (zh) * 2013-02-28 2013-05-08 南京航空航天大学 基于电磁感应的磁致伸缩高精度时间测量系统
CN106324633A (zh) * 2015-06-26 2017-01-11 无线电通信系统公司 Gnss应用中跟踪位置及速度的系统及方法

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CN116540518B (zh) * 2023-07-04 2023-10-13 云南电网有限责任公司 通过远方录波的继电保护装置时钟失步判定方法及系统

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US3898555A (en) * 1973-12-19 1975-08-05 Tempo Instr Inc Linear distance measuring device using a moveable magnet interacting with a sonic waveguide
US20070100570A1 (en) * 2005-10-28 2007-05-03 Teradyne, Inc. Dual sine-wave time stamp method and apparatus

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US4952873A (en) 1989-09-11 1990-08-28 Mts Systems Corporation Compact head, signal enhancing magnetostrictive transducer
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US6289294B1 (en) * 1999-02-17 2001-09-11 Daimlerchrysler Corporation Method for determining rotational data using an encoder device
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US3898555A (en) * 1973-12-19 1975-08-05 Tempo Instr Inc Linear distance measuring device using a moveable magnet interacting with a sonic waveguide
US20070100570A1 (en) * 2005-10-28 2007-05-03 Teradyne, Inc. Dual sine-wave time stamp method and apparatus

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100250184A1 (en) * 2008-03-18 2010-09-30 Satoshi Kawamura Rotation angle detection apparatus
DE112009000121B4 (de) * 2008-03-18 2013-09-26 Mitsubishi Electric Corp. Rotationswinkel-Erfassungsvorrichtung
CN103092061A (zh) * 2013-02-28 2013-05-08 南京航空航天大学 基于电磁感应的磁致伸缩高精度时间测量系统
CN106324633A (zh) * 2015-06-26 2017-01-11 无线电通信系统公司 Gnss应用中跟踪位置及速度的系统及方法

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EP2128570A1 (de) 2009-12-02

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